Most of us take for granted that the heat will come on when it’s cold, and the air conditioning will keep our homes cool in the summers, but have you ever stopped to think about how your HVAC system works? Understanding some basics of each system could help you troubleshoot if the need arises.
There are many components to a heating and cooling system and depending on whether you have an air conditioner [with a furnace] or a heat pump, the parts will vary. Here is a basic breakdown of the anatomy of an HVAC system.
Heating, ventilation, and air conditioning (HVAC) is a system of controlling indoor temperature, humidity, and indoor air quality. The main principles of the system are heat transfer, thermodynamics, and fluid mechanics.
Components of an HVAC System
- Thermostat: This is the part of the system you’ll interact with the most and be the most familiar with. It can be set manually to keep your home at your preferred temperature, or a “smart” programmable thermostat can adjust your home’s temperature even when you are not home, helping save on your energy bill.
- Burner: This is the device that starts your HVAC systems. The thermostat senses a temperature dip, and sends a signal to the burner component to start up the system.
- Furnace: The furnace, not to be confused with a boiler, is the epicenter of your HVAC system and is located inside your house, maybe in a utility closet or in the basement. Furnaces are large and typically require the most space out of all the other HVAC system components. The furnace’s job is to heat air, which then gets distributed to different parts of your home via ductwork or piping. Many homes have hybrid heating systems which combine the energy efficiency of heat pumps for milder weather with the powerful heating capability of a furnace for the more extreme cold temperatures.
- Boiler: A type of heating system that uses oil to heat water that turns into steam, which travels to radiators. A boiler heating system works well in multi-residence situations and is common in apartment buildings, multi-family dwellings, and older buildings or homes.
- Heat Exchanger: The heat exchanger is not part of the furnace but sits inside the furnace. It adds heat to the incoming air from the combustion chamber.
- Air Conditioner: In a central heating and cooling system, air conditioning is an essential component. Air conditioners provide cool air through ductwork inside your home by a method that draws warm air in from the outside and removing its heat.
- Condensing Unit: This unit is the outside portion of your air conditioner. Inside the cube-shaped unit, the condensing unit exchanges heat with the air that passes over it. Depending on the time of year it will release or collect that heat.
- Evaporator Coil: This HVAC equipment is also inside the furnace but does a different job than the heat exchanger. Inside the coil is refrigerant (a fluid that causes cooling). As warm air passes over the coil, it absorbs heat from the air and moves it outside. The cool air is then blown inside your home through the air ducts.
- Heat Pump: During the summertime, a heat pump is mechanically doing the same thing as air conditioners to cool your home, but how it warms your home in the wintertime is not the same. In the winter, a heat pump extracts heat from the outdoor air or ground and distributes it to your home.
- Refrigerant Lines. These metal tubes connect the evaporator coil with the condensing coil, which means the refrigerant tubes connect the indoor unit and outdoor unit of your HVAC systems. The tubes carry refrigerant to the condensing unit in the form of a gas.
- Vents: These are the outlets that help distribute heated air and cooled air from the duct system into the various rooms of your home. They’re generally found near the ceiling with angle slats, designed to send the air downward. It’s essential to ensure these vents don’t become blocked.
So how do these HVAC components work to cool and heat your house?
When the temperature in your home rises, your thermostat automatically turns on your air conditioning system. Warm air from the house is sucked in through the air return vents and into the furnace, where it blows across the evaporator coil. The cold refrigerant in the evaporator absorbs the heat from the air and turns into vapor inside the copper tubing. This process cools the air in the air handler, and the cooler air is then pushed through your ducts back into the living areas in your home.
Meanwhile, the refrigerant is pumped to the outdoor unit, where it is pressurized by the compressor and moves through the outside condenser coil. This process releases the heat outdoors with the help of a massive fan. After moving through the condenser, the refrigerant is expanded so it can be returned to the evaporator as a cold, low-pressure liquid. This cycle repeats until the cool air in your home drops in temperature enough that your thermostat turns off the HVAC system.
Furnace and Burner
When it’s time to heat your house, the furnace heats air in one area and distributes it throughout your home through a network of ducts and vents. The furnace starts when it receives the signal from the thermostat. The furnace valve opens and ignites the burner component beneath the combustion chamber. The valve works in conjunction with the thermostat to regulate the amount of oil that flows into the furnace. Flames from the burner component heat a metal heat exchanger. The heat circulates through the looped tubes of the heat exchanger, transferring the heat into the air. As heat is flowing through the heat exchanger, a motorized fan blows the heat through the ductwork and out through each room’s vents to heat your home.
The main principle of a boiler is to transfer heat to water by heating water or by producing steam that is then used to heat a home. Your thermostat senses a drop in your home’s temperature and triggers the boiler to turn on. Heat from the fuel source is then used to heat up the water inside the boiler. The heated water or steam gets sent throughout your home (via radiators) where it gives off its heat to warm the air. As the water cools (or the steam condenses), it travels back to the boiler where it’s reheated and sent back out to continue heating your home until it reaches the set temperature and your thermostat signals for the boiler to turn off.
Heat pumps can switch from air conditioning mode to heat mode by reversing the refrigeration cycle, which transforms the outside coil into the evaporator and the indoor coil into the condenser. The refrigerant flows through a closed system of refrigeration lines. Heat energy is absorbed from the outside air by the condenser coil and gets released inside by the evaporator coil. The air is then pulled into the ductwork by a fan, and the refrigerant is pumped from the interior coil to the exterior coil where it absorbs the heat. The warm air is then pushed through connecting ducts into air vents throughout your home, increasing the inside temperature. The refrigeration cycle is repeated until it reaches the desired temperature per the thermostat.
HOP Energy is the nation’s fastest growing residential and commercial full-service energy provider offering a wide selection of heating and air conditioning equipment. Their team of heating and cooling system experts will help you determine which HVAC system is right for you. With competitive pricing, top-notch 24/7 emergency service and a team of highly trained technicians, licensed and local to your area, you can see why more people are choosing HOP Energy for their energy needs.